1. Technical Field
The present invention relates to a liquid-jet head and a liquid-jet apparatus in which liquid droplets are ejected through a nozzle bored in a nozzle plate. More particularly, the invention relates to an ink-jet recording head and an ink-jet recording apparatus in which a part of a pressure generating chamber communicating with the nozzle is constructed from a vibration plate, and a piezoelectric element provided on the vibration plate is displaced to eject ink droplets through the nozzle.
The invention also relates to a method for producing a liquid-jet head in which liquid droplets are ejected through a nozzle bored in a nozzle plate. More particularly, the invention relates to a method for producing an ink-jet recording head in which a part of a pressure generating chamber communicating with the nozzle is constructed from a vibration plate, and a piezoelectric element provided on the vibration plate is displaced to eject ink droplets through the nozzle.
2. Related Art
A liquid-jet head for ejecting liquid droplets through a nozzle by imparting pressure to a liquid by a piezoelectric element or a heating element has been known, and its representative example is an ink-jet recording head for ejecting ink droplets. The ink-jet recording head, for example, has a structure in which a nozzle plate having nozzles for ejection of ink droplets is joined onto an ink chamber body having pressure converting elements for imparting pressure to ink, and a protective plate or a nozzle cover, which is a joining member, is joined onto the nozzle plate via an adhesive agent (see, for example, JP-A-5-201000 (FIG. 1, pages 3 to 4, etc.)).
With such an ink-jet recording head, metal components constituting the ink-jet recording head are charged by a recording medium such as recording paper, or static electricity from the outside, with the result that the pressure converting elements for imparting pressure to ink, or a driver IC or the like for driving the pressure imparting elements may be destroyed. Such a problem is apt to occur, particularly when the nozzle plate is formed from a metallic material. In the ink-jet recording head described in JP-A-5-201000, for example, the protective plate or the nozzle cover joined onto the nozzle plate via the adhesive agent is brought into contact with the nozzle plate at a contact portion different from the site of adhesion to establish conduction between the protective plate or the nozzle cover and a ground line, thereby suppressing charging of the nozzle plate.
With the ink-jet recording head of the earlier technology, moreover, the protective plate or the nozzle cover, which is the joining member, is joined onto the nozzle plate via the adhesive agent. If the adhesive agent oozes out or squeezes out, therefore, the adhesive agent may extend into the site of contact between the protective plate or the nozzle cover and the nozzle plate, causing insulation and making it impossible to suppress charging. The use of a film adhesive agent is conceivable to prevent oozing-out or squeezing-out, but control over the position of film adhesion is so difficult that the cost will increase. Oozing-out or squeezing-out may be prevented with the use of an adhesive agent having a spacer, such as beads, kneaded therein. However, quality control of the adhesive agent has to be exercised carefully to avoid dispersion or settlement of the spacer, rendering control difficult and resulting in cost increase.
If the nozzle plate is subjected to insulating, water repellent treatment, the applied ink repellent film needs to be partly removed for formation of a conductive portion, thereby increasing processing man-hours. Furthermore, the protective plate or the nozzle cover is conductive to the nozzle plate by contact. Thus, a clearance can be produced at the site of contact because of an environmental change, such as a temperature change. As a result, elimination of static electricity is not reliably carried out, thus rendering reliability dubious. Besides, an adhesion surface and a contact surface are required between the protective plate or the nozzle cover and the nozzle plate, posing the problem of upsizing the entire head.
Such problems are true of other liquid-jet heads for ejecting other liquids than ink, as well as the ink-jet recording head for ejecting ink.